1. Field of the Invention
The present invention relates to a method and arrangement for eliminating a ghost image in image forming apparatus utilizing a light beam such as a laser beam, and more particularly a method for eliminating a ghost image which appears, in a laser recording apparatus utilizing a rotary mirror, on a recording medium such as a photosensitive element or display element.
2. Description of the Prior Art
In an image forming apparatus in which a light beam from a laser is recorded, the use of the laser beam as the light source and the optical processing applied thereto inevitably results in the formation of various ghost images along the light path of said laser beam and also on the surface of the elements involved in such optical processing. Most ghost images move on the surface of the recording medium with the scanning beam, and the intensity thereof integrated in time is very weak. In case, however, of the use of a rotary mirror such as a polygonal mirror as the beam scanner in combination with a focusing lens and a recording medium, there is formed a stationary ghost image in spite of the fact that the laser beam is continuously moving. According to the intensity of the laser beam, such a ghost image will be provided with a significantly high time-integrated intensity and will therefore be rendered visible upon the formation of the image. Also if such a ghost image is avoided in a direction parallel to the scanning direction of said beam, the effective width of the recording medium becomes inevitably limited. In this manner, stated otherwise, there will inevitably be a limitation in the dimension of the recording medium or of the image to be formed thereon.